The present invention relates to an open-end wrench and, more particularly, to an open-end wrench having enhanced structural strength and a reduced volume suitable for driving a fastener in a limited space through a larger angle.
FIG. 1 shows a conventional open-end wrench 30 including a handle 31 and a jaw portion 32. Jaw portion 32 includes first and second engaging portions 321 and 322 and an opening 323 between first and second engaging portions 321 and 322. Opening 323 includes an arcuate bottom end 3231. First engaging portion 321 includes a first driving face 3211 on a side of opening 323, and second engaging portion 322 includes a second driving face 3221 on the other side of opening 323. First and second driving faces 3211 and 3221 are parallel to each other. A corner A3 is formed between bottom end 3231 of opening 323 and first driving face 3211. Another corner A4 is formed between bottom end 3231 of opening 323 and second driving face 3221. In use, the first and second driving faces 3211 and 3221 are engaged with a pair of parallel sides 22 of a fastener 20 having a corresponding size. Fastener 20 has six corners a-f. Bottom end 3231 abuts a corner d of fastener 20. A user can grip handle 31 and drive jaw portion 32 to rotate fastener 20 through engagement between first and second driving faces 3211 and 3221 and two parallel sides 22 of fastener 20. However, each of first and second driving faces 3211 and 3221 of open-end wrench 30 has a length L3, L4 that is much larger than the length of side 22 of fastener 20 such that a tip of each of first and second driving faces 3211 and 3221 will extend deep into a space in which fastener 20 is located. Furthermore, a width H3 from corner A3 of opening 323 to an outer surface of first engaging portion 321 is in proportion to length L3, and a width H4 from corner A4 of opening 323 to an outer surface of second engaging portion 322 is in proportion to length L4. Thus, widths H3 and H4 of open-end wrench 30 are relatively large due to the long lengths L3 and L4, causing restriction of use of open-end wrench 30 in limited spaces. Furthermore, rotation of open-end wrench 30 is often smaller than 60°. In some positions in a limited space, widths H3 and H4 may hinder disengagement of jaw portion 32 from fastener 20 for subsequent operation. Although the user may try to change the holding direction of open-end wrench 30, the operation is difficult or even impossible to proceed with further rotation of another 60°.
U.S. Pat. No. 5,074,171 discloses an open-end wrench with reduced size jaws. A distance between the throat recess and an imaginary line connecting the tips of the jaws is smaller than the across-flats dimension, preferably 0.86 times the across-flats dimension. Each jaw has a distance or maximum width at each of two corners of the throat recess. The maximum width defined between each of two driving faces to an associated outer surface of the jaw of the open-end wrench (corresponding to width H3, H4 of conventional open-end wrench 3 of a corresponding size) is smaller than conventional designs and is preferably 0.5 times the across-flats dimension. Thus, the open-end wrench of U.S. Pat. No. 5,074,171 has a reduced volume and a reduced weight as well as enhanced structural strength. However, the contact between the fastener and inner ends of the relief regions of the tips will cause damage to the serrated portions of the driving faces. Furthermore, the reduction in size of the open-end wrench of U.S. Pat. No. 5,074,171 is small, although the maximum width of each jaw at each corner of the throat recess is 0.5 times the across-flats dimension, providing little help in use of the open-end wrench in limited spaces. Further, the size reduction of the body of the open-end wrench of U.S. Pat. No. 5,074,171 is little, providing little reduction in the overall weight and the overall volume and still adversely affecting operation in limited spaces.